The sour and pungent smell of vinegar is because of acetic acid. Acetic acid is most well known because of its presence in vinegar, but it has many other uses. In this lesson, we will learn more about the structure, uses, and formula of acetic acid.
What is Acetic Acid?
Vinegar is a household essential often used for cooking, and it even helps unclog sinks.
What chemical substance makes vinegar smell the way it does? Vinegar is actually a solution that is made of 4-8% of acetic acid that is dissolved in water and other substances that give vinegar its flavor depending on its type.Acetic acid, also known as ethanoic acid and methanecarboxylic acid, is a colorless liquid that has a strong and distinct pungent and sour smell. Its chemical formula is C2H4O2: it has two carbon (C) atoms, four hydrogen (H) atoms and two oxygen (O) atoms. Because it has a carbon in its chemical formula, it is an organic compound. Its chemical formula can be written multiple ways, as shown here:C2H4O2CH3COOHCH3CO2HNow that we know the chemical formula of acetic acid, let’s talk about its chemical structure.
Its chemical structure is shown in the following illustration. Here, we can see two ways to draw its chemical structure (see video). On the left (1), all the carbon, hydrogen and oxygen atoms and how they are bonded to each other are shown. On the right (2), instead of writing the carbon atom, it is represented by an edge or bend in the line, and the hydrogen atoms attached to the first carbon on the left are not shown.
The chemical structure of carboxylic acid shows that the first carbon on the left has single bonds with three hydrogen atoms.
The second carbon, on the other hand, has a double bond with the oxygen atom and is singly bonded with the first carbon and the -OH group.Let’s take a closer look at the chemical structure of acid. Acetic acid is classified as a carboxylic acid. A carboxylic acid, shown as RCOOH, is a group of organic compounds that contain a carboxyl group.
Here, the R group in the carboxylic acid structure may contain one or more carbon and/or hydrogen atoms. A carboxyl group is the -COOH group boxed in red. Because acetic acid contains a carboxyl group as well, it is classified as a carboxylic acid. In fact, acetic acid is also known as the second simplest carboxylic acid. In the illustration, it also shows that the R group of acetic acid contains -CH3.
Each year, a million tons of acetic acid is produced. That is a lot! While we most commonly know that acetic acid is used in vinegar, it is used for so much more, and it is a very important chemical used in many industrial processes. Let’s take a look at the various uses of acetic acid.
Acetic Acid in Vinegar
Let’s start with acetic acid’s claim to popularity: vinegar. We use vinegar for so many things – for cooking, cleaning, laundry and many other household uses, like unclogging drains.
It is also used in a popular science project – the volcano science experiment – where the lava is vinegar reacting with baking soda colored in red food coloring. Vinegar is most definitely a cook’s friend. It is so important in the kitchen that we may even have many different types of vinegar: balsamic vinegar, apple cider vinegar, red and white wine vinegar, and more.
Production of Vinyl Acetate Monomer
A majority of the acetic acid that is produced is used to produce vinyl acetate monomer, or VAM. What is so important about VAM? Vinyl acetate monomer (VAM) is a building block that is used in many industries to make paints, adhesives, packaging, and more.
Production of Acetic Anhydride
Here is another major application of acetic acid; it is used to produce a chemical called acetic anhydride.
What is acetic anhydride used for? The major application of acetic anhydride is to make a substance called cellulose acetate, which is used to make a cellulose acetate film that is used in photography. Acetic anhydride is also used to produce heroin as well.
Production of Ester
Acetic acid also produces esters. Below, it shows some esters produced from acetic acid, like ethyl acetate and isobutyl acetate.
The esters from acetic acid are used in inks, paints, and coatings.
As a Solvent
Glacial acetic acid is a solution that contains 99% of acetic acid – a very high concentration! This chemical is used as a solvent in chemistry labs for different types of analysis and to remove impurities in chemicals.
Iontophoresis is a technology that uses a low level electric current to deliver drugs through our skin.
The medication that is delivered through the skin may help decrease muscle inflammation and calcium deposits in our muscles and tissue. What is the role of acetic acid here? It is used by the physical therapist as a solution in iontophoresis to treat physical ailments, like heel pain and frozen shoulder, where it works by decreasing the calcium deposits on the tendons of your shoulder.
Acetic acid, also known as ethanoic acid or methanecarboxylic acid, is a colorless liquid with a strong and distinct pungent and sour smell. Its chemical formula is C2H4O2 or can be written as CH3COOH or CH3CO2H. It is an organic compound that is classified as a carboxylic acid because a carboxyl (-COOH) group is present in its chemical structure. Acetic acid is also known as the second simplest carboxylic acid.
Acetic acid is most popularly known because of its use in vinegar. A majority of the acetic acid produced is used to produce vinyl acetate monomer (VAM), which is the building block to make paints, adhesives, packaging and more. Acetic acid is also used to produce acetic anhydride, which is used to produce heroin, and is also important to produce cellulose acetate films used in photography. Acetic acid also produces esters that are used in inks, paints, and coatings. In the chemistry laboratory, it is used as a solvent in many chemical reactions and for purifying chemicals. In medicine, acetic acid solution is used in iontophoresis to deliver drugs efficiently through the skin to treat various physical ailments.
Points to Remember
- Acetic acid is also known as ethanoic acid or methanecarboxylic acid
- Acetic acid is colorless, but its strong smell is pungent and sour
- Acetic acid products are used in the kitchen, photography, or medicine and are found in different industrial products
You should feel confident doing the following after completing this lesson:
- Describe the chemical structure of acetic acid
- Recite the characteristics of acetic acid
- List some of the uses of acetic acid and where it can be found